Inertial-based MEMS sensors, such as MEMS gyroscopes and accelerometers, are generally being used in greater quantities and in greater numbers of controls applications in automotive and vehicle systems. These applications may include, for example, usage in electronic stability controls (ESC), anti-lock braking systems (ABS), and supplemental restraint systems (SRS). Such sensors are also being used in various other applications, for example, in medical systems, such as in mechanized prostheses. In these and other MEMS applications, self-testing capability (also referred to as health monitoring) may be a beneficial if not a necessary feature to ensure that the MEMS sensor is operating properly within the application.
To ensure the proper operations of the MEMS sensor, those in the art have developed MEMS sensors with in-the-field self-testing capability. This self-test function generally entails injecting a known stimulus into the micro-electromechanical structure of a MEMS sensor during the initialization or startup operation of the sensor. As such, such self-test function may not observe a fault during the runtime operation.
Those in the art also have employed test function during the runtime operation of the sensor. The test stimulus of such runtime operation typically consists of an impulse response or a waveform that is applied outside the bandwidth or frequency of the stimulus of interest, which is generally a physical attribute intended to be observed by the MEMS sensors. As such, the test may provide an incomplete test of the MEMS sensor, as a portion of the potential bandwidth for measurement may be allotted for the testing function. Additionally, since the test is applied to a limited frequency range, the self-test function may, for example, fail to detect a defect that manifests in a specific frequency range. In particular, MEMS gyroscopes employed in ESC systems, for example, have been found to have certain linear and torsional vibration frequency that may not be measured concurrently with the operation of the self-test function.
Moreover, the bandwidth of a MEMS sensor is generally constrained by the design limitations and material properties of the micro-electromechanical structures. Thus, increasing the bandwidth of the MEMS sensor may require a redesign of the sensor, which may not be cost effective or possible.